The correct answer is C) ballasting appropriate port or starboard deep tanks. In a hazardous situation, you can generally improve the vessel's stability by transferring ballast to the appropriate port or starboard deep tanks. This helps shift the vessel's center of gravity and increase the righting moment, making the vessel more stable and less likely to capsize. The other options are incorrect because: A) pumping double bottoms to the forepeak would not improve stability, and D) deballasting double bottoms would reduce stability. Option B) transferring ballast athwart ships could potentially improve stability, but ballasting the port or starboard deep tanks is a more direct and effective way to enhance the vessel's stability in a hazardous situation.